Colorimetric determination of tin(II) levels in^99mTc labelling kits

Abstract

A rapid quantitative test for determination of stannous tin in kit preparations is described. After addition of phosphomolybdate a blue colour is measured at 700 nm. Sn²⁺ levels in pyrophosphate,mdp, dtpa, diethylhida, dimethylhida, glucoheptonate, phytate and tin colloid kits were determined. In many kits these levels proved to be rather low. Results from the colorimetric test were comparable with those obtained by iodometric titration. During exposure to the air by extensive stirring, Sn²⁺ preparations showed rapid deterioration which could be prevented by adding ascorbic acid.

This simple test is a valuable method to determine Sn²⁺ levels in many kit preparations and can be useful in the investigation of factors that contribute to the decrease of the Sn²⁺ content.